Departamento de Biotecnologia, Escola de Engenharia de Lorena, Universidade de São Paulo, 12602-810, Lorena, SP, Brazil.
Programa de Processos Tecnológicos e Ambientais, Universidade de Sorocaba, 18023-000 Sorocaba, SP, Brazil; Institute of Biology, University of Campinas (UNICAMP), 13080-655, Campinas, SP, Brazil.
Enzyme Microb Technol. 2019 Nov;130:109370. doi: 10.1016/j.enzmictec.2019.109370. Epub 2019 Jul 3.
Secretome evaluations of lignocellulose-decay basidiomycetes can reveal new enzymes in selected fungal species that degrade specific substrates. Proteins discovered in such studies can support biorefinery development. Brown-rot (Gloeophyllum trabeum) and white-rot (Pleurotus ostreatus) fungi growing in sugarcane bagasse solid-state cultures produced 119 and 63 different extracellular proteins, respectively. Several of the identified enzymes are suitable for in vitro biomass conversion, including a range of cellulases (endoglucanases, cellobiohydrolases and β-glucosidases), hemicellulases (endoxylanases, α-arabinofuranosidases, α-glucuronidases and acetylxylan esterases) and carbohydrate-active auxiliary proteins, such as AA9 lytic polysaccharide monooxygenase, AA1 laccase and AA2 versatile peroxidase. Extracellular oxalate decarboxylase was also detected in both fungal species, exclusively in media containing sugarcane bagasse. Interestingly, intracellular AA6 quinone oxidoreductases were also exclusively produced under sugarcane bagasse induction in both fungi. These enzymes promote quinone redox cycling, which is used to produce Fenton's reagents by lignocellulose-decay fungi. Hitherto undiscovered hypothetical proteins that are predicted in lignocellulose-decay fungi genomes appeared in high relative abundance in the cultures containing sugarcane bagasse, which suggests undisclosed, new biochemical mechanisms that are used by lignocellulose-decay fungi to degrade sugarcane biomass. In general, lignocellulose-decay fungi produce a number of canonical hydrolases, as well as some newly observed enzymes, that are suitable for in vitro biomass digestion in a biorefinery context.
木质纤维素降解担子菌的分泌组评估可以揭示特定真菌物种中降解特定底物的新酶。在这些研究中发现的蛋白质可以支持生物精炼厂的发展。在甘蔗渣固态培养中生长的褐腐菌（Gloeophyllum trabeum）和白腐菌（Pleurotus ostreatus）分别产生了 119 种和 63 种不同的细胞外蛋白。鉴定出的几种酶适合体外生物质转化，包括一系列纤维素酶（内切葡聚糖酶、纤维二糖水解酶和β-葡萄糖苷酶）、半纤维素酶（内切木聚糖酶、α-阿拉伯呋喃糖苷酶、α-葡萄糖醛酸酶和乙酰木聚糖酯酶）和碳水化合物活性辅助蛋白，如 AA9 溶菌多糖单加氧酶、AA1 漆酶和 AA2 多功能过氧化物酶。在这两种真菌中，还检测到细胞外草酸盐脱羧酶，仅在含有甘蔗渣的培养基中检测到。有趣的是，细胞内 AA6 醌氧化还原酶也仅在两种真菌的甘蔗渣诱导下产生。这些酶促进醌的氧化还原循环，这是木质纤维素降解真菌用来产生芬顿试剂的方法。迄今为止，在木质纤维素降解真菌基因组中预测的未被发现的假设蛋白在含有甘蔗渣的培养物中以高相对丰度出现，这表明木质纤维素降解真菌降解甘蔗生物质所使用的未被发现的新生化机制。一般来说，木质纤维素降解真菌产生许多典型的水解酶，以及一些新观察到的酶，这些酶适合在生物精炼厂的背景下进行体外生物质消化。
